Tooth eruption is a precisely timed and sequenced event which bring the tooth from an intraosseous position to a functional position in the oral cavity. Every structure of the developing tooth has been implicated in an eruption theory as a primary factor initiating this process but it appears that tooth eruption probably results from the interaction of several factors. The critical role of the dental follicle and type I collagen during tooth eruption has been strongly suggested. The hypothesis set forth in this proposal is that the process of tooth eruption is dependent on a differential and synchronized expression of gene products such as type I collagen in the dental follicle. We, therefore, hypothesize that the cells of the apical part of the dental follicle secrete type I collagen as a major component of the extracellular matrix whereas cells located in the coronal portion of the dental follicle stop expressing type I collagen as a pre-requisite to the initiation of tooth eruption. A divergence from this precisely regulated mechanism results in an inability of the teeth to erupt and leads to clinical impaction. In order to test our hypothesis, we will first establish in vivo the temporal and spatial expression of type I collagen in the dental follicle during pre-eruption and pre-functional phase of tooth eruption using immunological and acid nucleic probes and secondly establish in vitro the temporal and spatial expression of type I collagen in the coronal and apical portional of the dental follicle using immunological and nucleic acid probes. These two specific aims will be tested during a one year period to collect preliminary datas essential to the further understanding of the mechanism of tooth eruption and its regulation.